Addition of matrix metalloproteinase inhibition to conventional cytotoxic therapy reduces tumor implantation and prolongs survival in a murine model of human pancreatic cancer.
(73/1894)Matrix metalloproteinases (MMPs) participate in basement membrane degradation, a critical step in invasion of cancer cells. We have previously shown that MMP inhibition of pancreatic cancers improves survival and decreases MMP production in vivo. The purpose of this study was to determine whether BB-94 was better than cytotoxic therapy and would increase the efficacy of cytotoxic therapy (gemcitabine) in a murine model of human pancreatic cancer. A human pancreatic adenocarcinoma cell line (HPAC) was injected into the pancreata of BALB/c nu/nu mice. The mice were randomized 7 days after cancer cell injection to receive vehicle control, BB-94, gemcitabine, or gemcitabine and BB-94 until death or sacrifice at 84 days. At necropsy, tumors were harvested, and the relative enzyme activities of MMP-2 and MMP-9 were determined by gelatin zymography. Active MMP-2 levels in serum were determined using an ELISA technique. Combination treatment with gemcitabine and BB-94 significantly reduced implantation rates and improved survival in mice with documented orthotopic tumors compared with either therapy alone or control. Tumor levels of active and latent MMP-2 were higher than those of MMP-9 in both treated and control mice. There was a significant reduction of tumor MMP-2 activity in mice treated with BB-94, gemcitabine, or gemcitabine and BB-94. Serum levels of active MMP-2 were reduced in all treated groups, with the greatest reduction occurring in mice treated with gemcitabine and BB-94. Combination therapy with gemcitabine and BB-94 reduces cancer implantation and improves survival compared to treatment with BB-94, gemcitabine, or vehicle control alone. MMP production was reduced in all treated groups, reflecting reduced tumor progression, which was particularly seen with combination therapy with gemcitabine and BB-94. This study supports combining MMP inhibition with cytotoxic therapy (gemcitabine) for patients with pancreatic cancer. (+info)
Metalloproteinase inhibition reduces constrictive arterial remodeling after balloon angioplasty: a study in the atherosclerotic Yucatan micropig.
(74/1894)BACKGROUND: Arterial remodeling after balloon angioplasty has been recognized as a major determinant of restenosis. Perturbation of collagen metabolism might be important. After balloon injury, matrix metalloproteinase (MMP) expression is upregulated. We investigated the effect of Batimastat, a nonspecific MMP inhibitor, on late lumen loss, arterial remodeling, and neointima formation after balloon dilation. METHODS AND RESULTS: In atherosclerotic iliac arteries of 12 Yucatan micropigs, balloon dilation was performed, with intravascular ultrasound and quantitative angiography used before and after balloon dilation and at 42-day follow-up. The animals were randomly divided into 2 groups, the Batimastat group (n=6) and the vehicle group (n=6). All animals were intraperitoneally injected with either Batimastat or a vehicle immediately after balloon dilation and at 2 weeks and 4 weeks after balloon dilation. Angiographic and echographic late lumen loss in the Batimastat group versus the vehicle group was 0.3+/-0.1 versus 0.8+/-0.1 mm (P=0.01) and 2.2+/-0.5 versus 4.9+/-0.7 mm(2) (P=0.004), respectively. Late media-bounded area loss was used as a measure of remodeling after balloon dilation and was 0.9+/-0.6 mm(2) in the Batimastat group compared with 3.8+/-0.8 mm(2) in the vehicle group (P=0.003, mixed model analysis P=0.01). Neointima formation was 1.3+/-0.3 mm(2) in the Batimastat group and 1.0+/-0.2 mm(2) in the vehicle group (P=0. 542). CONCLUSIONS: Metalloproteinase inhibition by Batimastat significantly reduced late lumen loss after balloon angioplasty by inhibition of constrictive arterial remodeling, whereas neointima formation was not inhibited by MMP inhibition. (+info)
Differential inhibition of the prejunctional actions of angiotensin II in rat atria by valsartan, irbesartan, eprosartan, and losartan.
(75/1894)The effects of valsartan and other nonpeptide angiotensin II type 1 (AT(1)) receptor blockers on the prejunctional actions of angiotensin II were investigated in the isolated left atria of rat. Norepinephrine stores in rat atria were loaded with [(3)H]norepinephrine, and neuronal norepinephrine release was deduced from the radioactivity efflux. Angiotensin II (10(-9) to 10(-6) M) produced concentration-dependent enhancement of the electrical stimulation-induced efflux of [(3)H]norepinephrine from the preparation. Pretreatment of tissues with valsartan, irbesartan, eprosartan, or losartan (10(-8) to 10(-6) M) produced concentration-dependent inhibitions of the stimulation-induced efflux of radioactivity observed in the presence of angiotensin II (10(-7) M). The AT(1) receptor blockers did not decrease the "basal stimulation-induced overflow of radioactivity but rather selectively inhibited the angiotensin II-mediated augmentation of the response. Regression analyses of the inhibition of the angiotensin II-mediated response by valsartan, irbesartan, eprosartan, and losartan revealed corresponding log IC(50) values (log M, with 95% confidence intervals) of -7.78 (-8.19, -7.51), -7.65 (-8.02, -7.40), -7.12 (-7. 37, -6.86), and -6.75 (-7.00, -6.40), indicating that the IC(50) values for valsartan and irbesartan are significantly lower than those for eprosartan and losartan. Thus, valsartan is a potent inhibitor of the prejunctional facilitatory effect of angiotensin II on the release of norepinephrine from peripheral sympathetic nerves. This implies that the therapeutic domain of valsartan may be extended to include pathophysiological conditions such as congestive heart failure wherein prejunctional angiotensin II receptors apparently play a significant role. Whether the high potency of valsartan translates into a significant clinical advantage relative to the other agents tested remains to be ascertained. (+info)
Comparison of thymidylate synthase (TS) protein up-regulation after exposure to TS inhibitors in normal and tumor cell lines and tissues.
(76/1894)Thymidylate synthase (TS) is an important target for cancer chemotherapy. However, several mechanisms of resistance to TS inhibitors have been described. One mechanism that may be relevant to short-term exposure to TS inhibitors occurs as a result of disruption of the autoregulatory loop, which allows TS to control its own translation. This disruption leads to up-regulation of TS protein and is generally thought to decrease efficacy. This study has investigated TS protein up-regulation using a range of TS inhibitors in both tumor and nonmalignant cell lines in vitro and in vivo. Up-regulation of TS protein showed a time-, dose-, and cell-type-specific response to treatment with ZD9331. This response was observed in W1L2 cells treated for 24 h at equitoxic doses of raltitrexed (6-fold), ZD9331 (10-fold), fluorouracil (5-fold), LY231514 (7-fold), AG337 (7-fold), and BW1843U89 (3-fold). Up-regulation was observed over a range of doses. Elevation of TS protein only persisted up to 12 h after removal of drug. The extent of induction does not depend on basal TS levels. Nontransformed human fibroblasts showed significantly greater up-regulation of TS protein than tumor cells exposed to an equitoxic dose of ZD9331. In vivo experiments using the L5178Y thymidine kinase -/- mouse lymphoma implanted into DBA2 mice also showed greater up-regulation of TS protein in normal intestinal epithelial cells compared with tumor cells. These results confirm that TS up-regulation is a common feature of TS inhibition in tumor cells and that it may occur to a greater extent in normal tissues, although the clinical implications of these findings remain to be determined. (+info)
Stimulation of noradrenaline release by T-588, a cognitive enhancer, in PC12 cells.
(77/1894)Previously, we reported that (R)-(-)-1-(benzo[b]thiophen-5-yl)-2-[2-(N,N- diethylamino)ethoxy] ethanol hydrochloride (T-588), a novel putative cognitive enhancer, stimulated noradrenaline (NA) release from rat cerebral cortical slices. In this study, we investigated the effects of T-588 compared to other secretagogues on NA release from PC12 cells. Addition of as little as 10 microM T-588 stimulated [3H]NA release in a dose-dependent and an extracellular Ca(2+)-independent manner from PC12 cells. Ten micromolar ionomycin-, 300 microM adenosine-5'-O-(gamma-thiotriphosphate)- and 10 microM forskolin-induced extracellular Ca(2+)-dependent [3H]-NA release was further enhanced by 30 microM T-588. Cytosolic synaptophysin and 25-kDa synaptosome-associated protein immunoreactivity was increased by addition of T-588 in a dose-dependent manner. Interestingly, increases in synaptic vesicle-related proteins triggered by T-588 had a 4-min lag time and were completely dependent on extracellular CaCl2. These findings suggest that T-588 stimulates NA release from PC12 cells in a Ca(2+)-independent manner. T-588 also induced the translocation of synaptic vesicles in a Ca(2+)-dependent manner. (+info)
Fractalkine cleavage from neuronal membranes represents an acute event in the inflammatory response to excitotoxic brain damage.
(78/1894)Fractalkine is a recently identified chemokine that exhibits cell adhesion and chemoattractive properties. It represents a unique member of the chemokine superfamily because it is located predominantly in the brain in which it is expressed constitutively on specific subsets of neurons. To elucidate the possible role of neuronally expressed fractalkine in the inflammatory response to neuronal injury, we have analyzed the regulation of fractalkine mRNA expression and protein cleavage under conditions of neurotoxicity. We observed that mRNA encoding fractalkine is unaffected by experimental ischemic stroke (permanent middle cerebral artery occlusion) in the rat. Similarly, in vitro, levels of fractalkine mRNA were unaffected by ensuing excitotoxicity. However, when analyzed at the protein level, we found that fractalkine is rapidly cleaved from cultured neurons in response to an excitotoxic stimulus. More specifically, fractalkine cleavage preceded actual neuronal death by 2-3 hr, and, when evaluated functionally, fractalkine represented the principal chemokine released from the neurons into the culture medium upon an excitotoxic stimulus to promote chemotaxis of primary microglial and monocytic cells. We further demonstrate that cleavage of neuron-derived, chemoattractive fractalkine can be prevented by inhibition of matrix metalloproteases. These data strongly suggest that dynamic proteolytic cleavage of fractalkine from neuronal membranes in response to a neurotoxic insult, and subsequent chemoattraction of reactive immune cells, may represent an early event in the inflammatory response to neuronal injury. (+info)
Cloning and expression of genes encoding meta-cleavage enzymes from 4,6-dimethyldibenzothiophene-degrading Sphingomonas strain TZS-7.
(79/1894)Sphingomonas strain TZS-7 was reported as the first strain to have the ability to degrade 4,6-dimethyldibenzothiophene (4,6-dmDBT) by the ring-destructive pathway. Two genes for meta-cleavage dioxygenases were cloned from strain TZS-7. Expression of each gene showed that one enzyme was specific for 2,3-dihydroxybiphenyl while another was more specific for catechol. The genes for the two enzymes were named dmdC and catA. The analysis of deduced amino acid sequences indicates that CatA falls into the class of meta-cleavage dioxygenases acting on dihydroxylated monocyclic compounds and DmdC falls into the class of meta-cleavage dioxygenases acting on dihydroxylated polycyclic compounds. (+info)
A study of the intestinal absorption of an ester-type prodrug, ME3229, in rats: active efflux transport as a cause of poor bioavailability of the active drug.
(80/1894)The intestinal absorption of a prodrug is affected by a number of factors, such as its membrane permeability, stability in the gut lumen, and conversion to the parent drug in enterocytes. We evaluated the absorption of ME3229, an ester-type prodrug of a hydrophilic glycoprotein IIb/IIIa antagonist. Although the octanol/water distribution coefficient and permeability across a Caco-2 cell monolayer of ME3229 was high enough for us to expect good oral absorption, less than 10% of the dose was absorbed in rats. To clarify this unexpected outcome, we evaluated the rate of its disappearance from the gut lumen (V1), its degradation in the gut lumen (V(deg)), uptake into enterocytes (V(uptake)), and appearance in the mesenteric vein (V2) by using a single-pass perfusion technique in combination with an in vitro metabolism study. Our data suggested that ME3229 crossed the apical membrane and was taken up into enterocytes at a rate compatible with its lipophilicity, but that only a small fraction of the metabolites formed in enterocytes reached the mesenteric vein, primarily attributable to efflux into the intestinal lumen. Transport of the main metabolite across rat intestinal tissue mounted on an Ussing chamber suggested that an active efflux system pumped out any ionic metabolite(s) present. (+info)